The known apparatus for making a composite cable made of individual rectangular cross-sectioned strands has guide means for individual strands conveyed in two parallel stacks formed by lateral parallel guide surfaces; pressing elements, each of which extends perpendicular to the lateral guide surfaces and is engagable with a different stack, the two parallel stacks being conveyed between the two pressing elements which are displaceable in parallel oppositely to each other in a timed manner to press and release the stacks; and two nonrotatable pushing members mounted on the opposite lateral sides of the cable but pivotally displaced from the pressing elements, the pushing members being structured and positioned to be able to move across the conveying direction to displace at least one of the individual strands from each of the stacks to the other adjacent stack as well as bending the individual strand so displaced.
An apparatus having the above-mentioned features is described in British Patent 969,086. In this apparatus individual rectangular cross-sectioned strands pass through a roebling tool in stacks disposed in parallel beside each other and, as a result of the operation of the apparatus, a composite electrical cable is produced. The periphery of the strand formed by the stacked individual strands is engaged by pushing members, which displace top and bottom individual strands to the adjacent stack and bend the cable. This operation, which enables rectangular cross-sectioned strands to be twisted, is known as "roebling". The apparatus is called a "roebling" tool in honor of the inventor of the first roebling tool, Roebel.
In addition to two pushing members for displacing the top and bottom strand to the adjacent stack, the prior art roebling tool has two pressing elements, each of which pushes one of the stacks of individual strands upwards and downwards. On completion of the pushing of the stacks up or down, the pushing members engage the individual strands to displace them as described above. The course followed in the roebling of the individual strands of the composite cable and the composite cable is explained in detail, for example, in U.S. Pat. No. 2,249,509 and diagrammatically illustrated in FIG. 1a to 1c in the case of an even number of individual strands. FIG. 1a shows the starting condition of the two adjacent stacks of individual strands 1 of rectangular cross-section. The individual strands 1 are moved toward and somewhat past each other by the thickness of an individual strand by engagement of pressing elements, which engage on the top and bottom of the respective two stacks (in the direction indicated by arrows 2 in FIG. 1b). The top and bottom individual strands are then immediately displaced by pushing members onto the respective adjacent stack (in the direction indicated by arrow 3 in FIG. 1c). At the same time the two individual strands acted on by the pushing members are bent. FIG. 2 shows in perspective a composite cable in which the top and bottom individual strands are each bent, the bending places being denoted by reference number 4.
One disadvantage of the prior art apparatus is that the bending length--i.e. the length from start to end of a bend--is comparatively large. With equal length of step--i.e. the distance between successive bends--this leads to correspondingly short parallel sections of the individual strands, resulting in a deterioration in winding properties, especially in the case of composite cable having a large number of individual strands. If the parallel portions of the individual strands are lengthened, the length of step becomes correspondingly longer, and this also causes the winding properties to deteriorate.